The present invention relates to fluid coupling devices of the type including valve means operable to control the quantity of fluid in the fluid operating chamber. More particularly, the present invention relates to fluid coupling devices of the type including a valve element which is actuated to move in an axial direction between the open and closed positions.
Although the present invention may be utilized with various types of fluid coupling devices, it is especially adapted for use in remotely actuated fluid coupling devices, and will be described in connection therewith. In a remotely actuated coupling, movement of the valve element is normally in an axial direction, because movement of the valve is usually achieved by means of a device such as a solenoid or fluid pressure piston arrangement which inherently has an axial output movement.
Although the present invention may be utilized in fluid coupling devices having any type of axial actuation, it is especially adapted for use with some form of fluid pressure actuation, and will be described in connection therewith.
In many vehicle applications of fluid coupling devices, it is preferable to use rear actuation of the valve element, i.e., to actuate the valve element by means of a fluid pressure piston which is pressurized from the rear or water pump side of the coupling.
It is also desirable in many vehicle applications to provide a fluid coupling device which is "fail-safe," i.e., will operate in the relatively high speed, engaged mode in the absence of the external actuation input, such as the fluid pressure signal. Thus, if the source of fluid pressure fails, the coupling device will continue to operate in the engaged mode to prevent overheating of the vehicle engine.